Branch circuit load calculation kitchen equipment

[brother]

Had a situation where I found a microwave, coffee pot, and toaster on the same circuit. I let the people know that the microwave itself needs to have its own circuit, since its almost 14 amps. Toaster at 13.75 amps coffee pot at 7.8 amps.

I suggested they go ahead add another circuit since the toaster and coffee pot would be on the same one even after the microwave is dedicated, and its no doubt someone will plug more things in on the counter top like they have in the past, this in a break room.

Someone asked me about demand factor for these 2 cooking units. Unless I'm missing something, I told them they have to use the actual nameplate kw, you cannot use the demand factors in table 220.55 because these 2 are below 1 3/4 kw (1.75 X 1000=1750) per note 3. Toaster 13.75 x 120=1650 kw , coffee pot 7.8 x 120=936 kw.

But , It's been awhile since I did these kitchen equipment calcs for branch circuits since I always added another circuit for these type of situations anyways because its no real cost. Did I tell them correctly?

Does note 4 come into play here? I do not consider these to be counter-mounted cooking units, they sit on the counter, they are not mounted as another person tried to imply. This is commercial break room, not a dwelling unit.

 

[Hv&Lv]

This is commercial break room, not a dwelling unit.

I would say 220.56 should be used for this.

I have never used 220.55 for a toaster or a coffee pot.

Either way, the circuit is overloaded. Using the demand factor it is over 30 amps.
With the microwave separate, the circuit is still over 20 amps.

 

[Smart $]

... Did I tell them correctly?

Does note 4 come into play here? ....

I would say 220.56 should be used for this.

....

Demand factors in or after 220.40 are for service and feeder conductors... not branch circuits. However, there are a few instances for branch-circuit load calculations which permit using the demand factors. For instance...

220.14(B) Electric Dryers and Electric Cooking Appliances in
Dwelling Units. Load calculations shall be permitted as
specified in 220.54 for electric dryers and in 220.55 for
electric ranges and other cooking appliances.

But as OP stated, his scenario is a break room, not a dwelling unit.

As a side note, countertop cooking appliances are considered counter-mounted.

Cooking Unit, Counter-Mounted. A cooking appliance
designed for mounting in or on a counter and consisting of
one or more heating elements, internal wiring, and built-in
or mountable controls.

In summary, there is no demand factor that can be applied to the OP circuit(s).

 

[brother]

Demand factors in or after 220.40 are for service and feeder conductors... not branch circuits. However, there are a few instances for branch-circuit load calculations which permit using the demand factors. For instance...



But as OP stated, his scenario is a break room, not a dwelling unit.

As a side note, countertop cooking appliances are considered counter-mounted.



In summary, there is no demand factor that can be applied to the OP circuit(s).

So Basically I am right in telling them to use the nameplate kw to do the calculation. 2008 NEC 220.14(A) would validate this for branch circuits plugging in the toaster and coffee pot in the same circuit is a code violation in a commercial setting!

 

[Smart $]

So Basically I am right in telling them to use the nameplate kw to do the calculation. 2008 NEC 220.14(A) would validate this for branch circuits plugging in the toaster and coffee pot in the same circuit is a code violation in a commercial setting!

At the load values you provided, I agree.

 

[david luchini]

So Basically I am right in telling them to use the nameplate kw to do the calculation. 2008 NEC 220.14(A) would validate this for branch circuits plugging in the toaster and coffee pot in the same circuit is a code violation in a commercial setting!

Assuming this is a 20A multi-outlet receptacle branch circuit, I don't see any violation with the one circuit having the microwave, toaster, and coffee maker plugged into it. Granted, it won't be very practical since they won't be able to use more than one appliance at a time.

210.23(A)(1) says the rating of any one cord-and-plug connected equipment not fastened in place shall not exceed 80% of the branch circuit rating. If the largest cord-and-plug connected equipment is the microwave (at 14 Amps), that does not exceed 80% of the branch circuit rating.

I do not believe 220.14(A) would apply. This is not a branch circuit for a specific appliance, but rather a "general-purpose branch circuit" (see Art. 100 definitions.)

 

[brother]

Assuming this is a 20A multi-outlet receptacle branch circuit, I don't see any violation with the one circuit having the microwave, toaster, and coffee maker plugged into it. Granted, it won't be very practical since they won't be able to use more than one appliance at a time.

210.23(A)(1) says the rating of any one cord-and-plug connected equipment not fastened in place shall not exceed 80% of the branch circuit rating. If the largest cord-and-plug connected equipment is the microwave (at 14 Amps), that does not exceed 80% of the branch circuit rating.

I do not believe 220.14(A) would apply. This is not a branch circuit for a specific appliance, but rather a "general-purpose branch circuit" (see Art. 100 definitions.)

I know we are splitting hairs here, and analyzing code language, but this is a 'break room with counter top' specifically for these appliances use. At least thats the way I would interpet it.

So that would not be general purpose.

 

[north star]

+ + +

...or they can just wait until after the fire to correct it!

+ + +

 

[david luchini]

I know we are splitting hairs here, and analyzing code language, but this is a 'break room with counter top' specifically for these appliances use. At least thats the way I would interpet it.

And if they take the microwave out and put a coffee grinder in, is the circuit still specifically for the microwave appliance? The circuit is general-purpose for whatever they want to plug into it. The definition of general purpose branch circuit is a branch circuit that supplies two or more receptacles or outlets for lighting and APPLIANCES.

The branch circuit for the break room counter top is for plugging in appliances, whatever appliances they might desire. It could be the microwave, toaster and coffee maker. It could be the coffee maker and a hot plate. It could be the toaster and a CD player. It is not a circuit that is specific to microwave, toaster and coffee maker in the OP.

The only thing the code has to say about what gets plugged in is that any one item cannot have a load greater than 80% of the branch circuit rating.

 

[Hv&Lv]

Demand factors in or after 220.40 are for service and feeder conductors... not branch circuits.

I missed the part about branch circuits, although I disagree about 220.54 & 220.55 being for feeders and service conductors only. Those two are also for branch circuits.

 

[Smart $]

I missed the part about branch circuits, although I disagree about 220.54 & 220.55 being for feeders and service conductors only. Those two are also for branch circuits.

220.54 & 220.55 can be used for [dwelling unit] branch circuits because 220.14(B) says you can use them... not because they are specifically for branch circuits.

 

[kwired]

Assuming this is a 20A multi-outlet receptacle branch circuit, I don't see any violation with the one circuit having the microwave, toaster, and coffee maker plugged into it. Granted, it won't be very practical since they won't be able to use more than one appliance at a time.

210.23(A)(1) says the rating of any one cord-and-plug connected equipment not fastened in place shall not exceed 80% of the branch circuit rating. If the largest cord-and-plug connected equipment is the microwave (at 14 Amps), that does not exceed 80% of the branch circuit rating.

I do not believe 220.14(A) would apply. This is not a branch circuit for a specific appliance, but rather a "general-purpose branch circuit" (see Art. 100 definitions.)

I know we are splitting hairs here, and analyzing code language, but this is a 'break room with counter top' specifically for these appliances use. At least thats the way I would interpet it.

So that would not be general purpose.

And if they take the microwave out and put a coffee grinder in, is the circuit still specifically for the microwave appliance? The circuit is general-purpose for whatever they want to plug into it. The definition of general purpose branch circuit is a branch circuit that supplies two or more receptacles or outlets for lighting and APPLIANCES.

The branch circuit for the break room counter top is for plugging in appliances, whatever appliances they might desire. It could be the microwave, toaster and coffee maker. It could be the coffee maker and a hot plate. It could be the toaster and a CD player. It is not a circuit that is specific to microwave, toaster and coffee maker in the OP.

The only thing the code has to say about what gets plugged in is that any one item cannot have a load greater than 80% of the branch circuit rating.

I was going to agree with the first quote from David here, and reply to brother, then David replied and mostly said what I wanted to say. So I guess I have nothing to say that hasn't been said already

 

[Smart $]

...

210.23(A)(1) says the rating of any one cord-and-plug connected equipment not fastened in place shall not exceed 80% of the branch circuit rating. If the largest cord-and-plug connected equipment is the microwave (at 14 Amps), that does not exceed 80% of the branch circuit rating.

...

While I agree the 80% limitation for one connected load is noteworthy, can you show me where the code allows you to knowingly connect two or more loads to a multi-outlet receptacle circuit to exceed 100%...?

While you look for that...

210.20 Overcurrent Protection. Branch-circuit conductors
and equipment shall be protected by overcurrent protective
devices that have a rating or setting that complies
with 210.20(A) through (D).

(A) Continuous and Noncontinuous Loads. Where a
branch circuit supplies continuous loads or any combination
of continuous and noncontinuous loads, the rating
of the overcurrent device shall not be less than the noncontinuous
load plus 125 percent of the continuous load.

 

[Hv&Lv]

220.54 & 220.55 can be used for [dwelling unit] branch circuits because 220.14(B) says you can use them... not because they are specifically for branch circuits.

Yes I understand that. That is the reason for "Those two are also for branch circuits."

 

[kwired]

My take on this installation is whenever I am doing a similar installation, you may have an idea that a microwave or coffee pot may be intended in a particular location, otherwise you really don't know what will be plugged in in these areas.

That said it is not a code violation to only have one circuit unless maybe it is known what loads will be there, but it also is in many cases just poor design to not have more than one circuit to a location like this, as the chance of having multiple appliances that draw similar loads as mentioned here is pretty good.

Question for OP, has this circuit been giving them tripping problems, or do they just know they have to watch what runs at one time?

Surprisingly this possibly may not have much breaker tripping problems - just depends on how the appliances normally get used. Coffee maker probably draws hard and longer duration while brewing, but otherwise maybe not so much when just maintaining heat in the pot. Microwave and toaster may not run at same time very often if ever, kind of depends on how many people typically use this break room at one time and just how much they actually use these appliances.

 

[david luchini]

While I agree the 80% limitation for one connected load is noteworthy, can you show me where the code allows you to knowingly connect two or more loads to a multi-outlet receptacle circuit to exceed 100%...?

Can you show me where the code prohibits you from knowingly connecting two or more loads to a multi-outlet receptacle circuit to exceed 100%? It doesn't. It wouldn't be enforceable. Supposed you had a branch circuit in an office space that was designed for an intended load of a desktop computer, monitor, and table lamp. But the end users plug in 4 computers, 8 monitors, and 4 ipod chargers 3 cell phone chargers and 2 electric space heaters. The circuit is going to be overloaded, but the code can't prevent the end user from plugging all of that load into the circuit. The code can make sure that the circuit is properly protected against that overload so it doesn't start a fire.

It is the same with the counter top receptacles in the OP. All three of the appliances can be plugged in, and any one can be operated at a time. And there will be no problems as long as only one appliance is used at a time. As soon as two appliance are used together, the circuit will be overloaded. The circuit should be properly protected by code requirements to make sure the overload doesn't do any harm.

 

[brother]

My take on this installation is whenever I am doing a similar installation, you may have an idea that a microwave or coffee pot may be intended in a particular location, otherwise you really don't know what will be plugged in in these areas.

That said it is not a code violation to only have one circuit unless maybe it is known what loads will be there, but it also is in many cases just poor design to not have more than one circuit to a location like this, as the chance of having multiple appliances that draw similar loads as mentioned here is pretty good.

Question for OP, has this circuit been giving them tripping problems, or do they just know they have to watch what runs at one time?

Surprisingly this possibly may not have much breaker tripping problems - just depends on how the appliances normally get used. Coffee maker probably draws hard and longer duration while brewing, but otherwise maybe not so much when just maintaining heat in the pot. Microwave and toaster may not run at same time very often if ever, kind of depends on how many people typically use this break room at one time and just how much they actually use these appliances.

To answer your question, this is a new building with new counter top receptacles for the coffee pot and toaster etc.. . The microwave has it own dedicated circuit as it has a special cabinet for it that was knowingly designed that way. They just put it in, but I was letting them know they will have a breaker tripping if they run those other cooking units, coffee pots and toasters etc.. at the same time on the other outlets as that was what they were planned for. I still see this as a code violation because they intended and knew what loads will be there... ie.. the toaster and coffee pot, and most likely more because history has shown that.

Can you show me where the code prohibits you from knowingly connecting two or more loads to a multi-outlet receptacle circuit to exceed 100%? It doesn't. It wouldn't be enforceable.

I respectfully disagree, here are the articles. And remember these are not general purpose receptacles.

2008 NEC 210.11 Number of Branch Circuits. The minimum number of branch circuits shall be determined from the total calculated load and the size or rating of the circuits used. In all installations, the number of circuits shall be sufficient to supply the load served. In no case shall the load on any circuit exceed the maximum specified by 220.18

210.19(A)(1) General. Branch circuit conductors shall have an ampacity not less than the maximum load to be served.....
220.18 Maximum Loads. The total load shall not exceed the rating of the branch circuit....

It is a code violation to knowingly connect loads you know will exceed 100% of the branch circuit, i.e. trip the breaker!

 

[Smart $]

Can you show me where the code prohibits you from knowingly connecting two or more loads to a multi-outlet receptacle circuit to exceed 100%? It doesn't. ...

It does... and I already did. Here it is again...

210.20 Overcurrent Protection. Branch-circuit conductors
and equipment shall be protected by overcurrent protective
devices that have a rating or setting that complies
with 210.20(A) through (D).

(A) Continuous and Noncontinuous Loads. Where a
branch circuit supplies continuous loads or any combination
of continuous and noncontinuous loads, the rating
of the overcurrent device shall not be less than the noncontinuous
load plus 125 percent of the continuous load.

I'll bet the OP loads are not being unplugged from the circuit while not in use. They are therefore simultaneously-connected loads. Whether they are operated simultaneously or not does not matter. The fact they could be is all that matters.

I agree situations as you describe occur all the time on general purpose receptacle circuits which had no known [or expected] load at the design stage... but that's as far as I'll go in agreeing with you.

 

[Smart $]

...

It is a code violation to knowingly connect loads you know will exceed 100% of the branch circuit, i.e. trip the breaker!

It does not even have to trip the breaker. In most cases a non-continuous load of 101% will not trip a breaker.

 

[kwired]

It does not even have to trip the breaker. In most cases a non-continuous load of 101% will not trip a breaker.

200% load will not trip breaker if only for short duration, which is why this may surprisingly not have as much breaker tripping as some might expect.